Ahmed Issack Hassan, chairman for Kenya's Independent Electoral and Boundaries Commission, said elections in five wards out of an estimated 1,450 would be rescheduled because of errors with some ballots.
"We have been forced to call off elections in these areas because of mix up in the ballot papers," he was quoted by Kenyan newspaper the Daily Nation as saying. "In some cases we have missing names of candidates while in other cases names have been interchanged."
Kenyans lined up at polling stations Monday for national elections, the first under laws enacted after a deadly 2007 contest.
Thousands of people were killed following 2007 elections amid clashes between supporters of outgoing President Mwai Kibaki and challenger Raila Odinga, the prime minister competing in this year's presidential contest.
The United Nations and others in the human rights community expressed concern there may be a repeat of the 2007 melee. Odinga said Monday that he received an apology from the Financial Times newspaper for misrepresenting his claims that there would be trouble should he lose the election.
At least 12 people were killed in clashes between police and a secessionist group overnight, reports al-Jazeera. The broadcaster adds, however, that the violence wasn't associated with the elections.
There was no word on results or rescheduling.